The present invention relates to processes for conjointly producing bromine and a concentrated aqueous solution of calcium chloride.
Bromine is useful in a wide range of industries. For example, bromine is used in the manufacture of brominated flame retardants such as tetrabromobisphenol, decabromodiphenylethane, decabromodiphenyloxide, and brominated polystyrenes. Bromine is also used, e.g., in the manufacture of 1,2-dibromoethane, which is used as a petrol additive, in the manufacture of compounds used in photography (e.g. silver bromide, which is the light sensitive material in film), in the manufacture of dyestuffs and drugs, in analytical laboratory in testing for unsaturation in organic compounds, as a disinfectant, and in gold extraction. Calcium chloride is also useful in numerous applications, e.g., as a drying agent, in ice and dust control, in oil well drilling, in food processing, in concrete mixtures to speed up setting, as an additive in plastics, and as a drainage aid for wastewater treatment.
One source used in production of bromine and calcium chloride is brine. Brine is an aqueous solution nearly saturated with halide salts and which is produced in several areas of the United States. Such produced brines typically contain at least sodium chloride, sodium bromide and calcium chloride. Additionally, certain processes, such as processes for producing brominated flame retardants, generate substantial quantities of hydrogen bromide as a by-product, which can be converted to bromine.
Processes for production of bromine from these and other bromide-containing solutions are well know. For example, bromine can be produced by a bromine steaming out process, such as Kubierschky's distillation method, see, e.g., Kirk-Othmer, Encyclopedia of Chemical Technology, Fourth Edition, volume 4, pages 548 through 553. Other methods for recovering bromine from bromide-containing solutions are described, e.g., in U.S. Pat. No. 3,181,934, U.S. Pat. No. 4,719,096, U.S. Pat. No. 4,978,518, U.S. Pat. No. 4,725,425, U.S. Pat. No. 5,158,683, and U.S. Pat. No. 5,458,781.
Processes for production of calcium chloride from brines and other sources are also well known. See, e.g., U.S. Pat. No. 4,704,265, WO 03/035550, and U.S. Pat. No. 6,524,546.
Even in view of these and other published methods for production of bromine and for production of calcium chloride, it would be commercially beneficial to have processes for conjointly producing bromine and calcium chloride.